CROSS VALIDATION OF A SENSORY LANGUAGE FOR CHEDDAR CHEESE

Communication and replication of sensory data from different sites are important to track progress on fundamental research issues and to ensure that research efforts are not duplicated. A uniform anchored Cheddar cheese sensory language has previously been identified and refined. The objective of this study was to demonstrate application of the defined sensory language for Cheddar cheese for communication between sensory panels at three different sites. The defined and referenced sensory language for Cheddar cheese was disseminated to panel leaders at the three sites and sensory panels (n ≤ 8) were trained for 40 to 80 h at each site. Ten forty-pound blocks of Cheddar cheese representing different ages were collected and evaluated by the panels. Cheeses were differentiated by the three panels by univariate and multivariate analysis (P<0.05). Cheeses were differentiated by the three panels in a similar manner. Results indicate that it is possible to calibrate panels using a standardized defined sensory language.     

Biotechnological methods to accelerate cheddar cheese ripening

Cheese is one of the dairy products that can result from the enzymatic coagulation of milk. The basic steps of the transformation of milk into cheese are coagulation, draining, and ripening. Ripening is the complex process required for the development of a cheese's flavor, texture and aroma. Proteolysis, lipolysis and glycolysis are the three main biochemical reactions that are responsible for the basic changes during the maturation period. As ripening is a relatively expensive process for the cheese industry, reducing maturation time without destroying the quality of the ripened cheese has economic and technological benefits. Elevated ripening temperatures, addition of enzymes, addition of cheese slurry, attenuated starters, adjunct cultures, genetically engineered starters and recombinant enzymes and microencapsulation of ripening enzymes are traditional and modern methods used to accelerate cheese ripening. In this context, an up to date review of Cheddar cheese ripening is presented.     

Spatial and temporal distribution of non-starter lactic acid bacteria in Cheddar cheese

AIMS: The aim of this work was to investigate the spatial and temporal distribution of species and strains of non-starter lactic acid bacteria (NSLAB) within Cheddar cheese. METHODS AND RESULTS: Randomly amplified polymorphic DNA was used to identify and track the principle species and strain groups of NSLAB present. The same strains dominated each location examined within a cheese at any particular time point. Temporal change in species and strains of NSLAB during ripening was observed. A mixture of Lactobacillus paracasei, Lact. plantarum, Lact. rhamnosus and unidentified strains was found up to 6 weeks of maturation, thereafter only Lact. paracasei strains were isolated. CONCLUSION: Little variation in the spatial distribution of NSLAB strains occurs within Cheddar cheese; however, temporal changes in the species and strains were observed during ripening. SIGNIFICANCE AND IMPACT OF THE STUDY: The complex changes in the composition of the NSLAB community of Cheddar cheese may be the source of the variation in flavour that is seen in commercial practice.     

Biotechnological Methods to Accelerate Cheddar Cheese Ripening

ABSTRACT

Cheese is one of the dairy products that can result from the enzymatic coagulation of milk. The basic steps of the transformation of milk into cheese are coagulation, draining, and ripening. Ripening is the complex process required for the development of a cheese's flavor, texture and aroma. Proteolysis, lipolysis and glycolysis are the three main biochemical reactions that are responsible for the basic changes during the maturation period. As ripening is a relatively expensive process for the cheese industry, reducing maturation time without destroying the quality of the ripened cheese has economic and technological benefits. Elevated ripening temperatures, addition of enzymes, addition of cheese slurry, attenuated starters, adjunct cultures, genetically engineered starters and recombinant enzymes and microencapsulation of ripening enzymes are traditional and modern methods used to accelerate cheese ripening. In this context, an up to date review of Cheddar cheese ripening is presented.     

TASTE COMPONENTS OF CHEDDAR CHEESE: FRACTIONATION AND OPTIMIZATION OF CHEDDAR CHEESE TASTE IN WATER

To determine the taste components of Cheddar cheese, we fractionated one mild Cheddar cheese and one aged Cheddar cheese by water extraction, freeze‐drying and gel filtration. Salty, sour and umami were the three predominant tastes present in the fractions. Neither trigeminal sensations nor astringency was perceived. We used response surface methodology to reconstruct a mild Cheddar cheese taste and an aged Cheddar cheese taste in water. Less salt and less acid were needed to simulate the taste of mild Cheddar cheese, compared with aged Cheddar cheese. Our optimized water solutions (containing sodium chloride, lactic acid and monosodium glutamate) were as similar to the real cheese samples as were the water extracts of the standard cheeses. However, neither our optimized solutions nor the water extracts matched the taste of the actual cheeses.     

Evaluation of culture media for the recovery of Mycobacterium avium subsp. paratuberculosis from Cheddar cheese

AIMS: The study evaluated the efficacy of four Mycobacterium avium subsp. paratuberculosis (MAP) culture media in suppressing commonly used starter cultures and typical nonstarter microflora present during the manufacture and ripening of Cheddar cheese, with a view to identify a suitable medium for the enumeration of MAP during laboratory-scale Cheddar production. METHODS AND RESULTS: Four Cheddar starter cultures and Cheddar cheese manufactured with these starters were inoculated onto Herrold's egg yolk medium (HEYM); HEYM supplemented with vancomycin, amphotericin B and nalidixic acid (HEYM/VAN); Middlebrook 7H10 agar containing polymyxin, amphotericin B, nalidixic acid, trimethoprim and azlocillin (PANTA) antibiotic supplement; and BACTEC 12B radiometric medium with and without a preliminary decontamination step (0.75% w/v hexadecylpyridinium chloride (HPC), 5 h). The inclusion of a decontamination step inhibited all Cheddar cheese starter and nonstarter micro-organisms. The medium 7H10/PANTA and to a lesser extent HEYM/VAN were effective inhibitors of cheese microflora when no decontamination step was employed. CONCLUSIONS: Middlebrook 7H10 medium, supplemented with PANTA antibiotics, suppressed all micro-organisms associated with ripening Cheddar cheese manufactured with pasteurized milk. SIGNIFICANCE AND IMPACT OF THE STUDY: A MAP culture medium has been identified, which may be used to enumerate this bacterium during the laboratory manufacture and ripening of Cheddar cheese and hence facilitate further research into the persistence of this pathogen in the product.     

CHANGES IN THE PERCEIVED TEXTURAL PROPERTIES OF CHEDDAR CHEESE DURING MATURATION

The perceived textural attributes of an English Cheddar were measured by a trained panel at various intervals during ripening, including those corresponding to mild and medium maturation times for this variety. The moisture content and pH were also monitored. After the recommended ripening period of 50 weeks the matured cheese was significantly less springy, firmer, harder, crumblier and creamier, indicating that textural attributes are related to the age of the Cheddar. Measures beyond the recommended maturation period revealed further significant differences. Comparisons of the measures taken at mild, medium and full maturity also revealed differences in the textural properties of the different classes of Cheddar. Significant correlations (p ≥0.01) between pH and springiness, crumbliness by fingers and creaminess suggested a strong relationship between these textural attributes and the extent of proteolysis. The results of this study revealed a strong relationship between age and the textural attributes of cheddar when restricted to one particular variety.     

Contribution of Lactococcus lactis cell envelope proteinase specificity to peptide accumulation and bitterness in reduced-fat Cheddar cheese

Bitterness is a flavor defect in Cheddar cheese that limits consumer acceptance, and specificity of the Lactococcus lactis extracellular proteinase (lactocepin) is widely believed to be a key factor in the development of bitter cheese. To better define the contribution of this enzyme to bitterness, we investigated peptide accumulation and bitterness in 50% reduced-fat Cheddar cheese manufactured with single isogenic strains of Lactococcus lactis as the only starter. Four isogens were developed for the study; one was lactocepin negative, and the others produced a lactocepin with group a, e, or h specificity. Analysis of cheese aqueous extracts by reversed-phase high-pressure liquid chromatography confirmed that accumulation of alpha(S1)-casein (f 1-23)-derived peptides f 1-9, f 1-13, f 1-16, and f 1-17 in cheese was directly influenced by lactocepin specificity. Trained sensory panelists demonstrated that Cheddar cheese made with isogenic starters that produced group a, e, or h lactocepin was significantly more bitter than cheese made with a proteinase-negative isogen and that propensity for bitterness was highest in cells that produced group h lactocepin. These results confirm the role of starter proteinase in bitterness and suggest that the propensity of some industrial strains for production of the bitter flavor defect in cheese could be altered by proteinase gene exchange or gene replacement.     

Cheddar cheese cooking temperature induces differential lactococcal cell permeabilization and autolytic responses as detected by flow cytometry: implications for intracellular enzyme accessibility

AIMS: To determine the influence of cheese cooking temperature on autolysis and permeabilization of two lactococcal starter strains in broth and in Cheddar cheese juice during ripening. METHODS AND RESULTS: Flow cytometry (FCM) was used to identify and enumerate intact and permeabilized cells in broth and in Cheddar cheese juice. Levels of intracellular enzyme activities were quantified concurrently. Permeabilized cell numbers increased for both strains in broth following a temperature shift from 32 to 38 degrees C and was accompanied by an increase in the level of accessible intracellular enzyme activities. The relative proportions of intact and permeabilized cell populations, as detected by FCM in cheese juice, changed during 42-day ripening. Permeabilized cell populations increased during ripening for both strains; however, an increase in accessible intracellular enzyme activity was observed only for the highly autolytic strain Lactococcus lactis AM2. CONCLUSIONS: Differences in the autolytic and permeabilization response induced by cooking temperature in two lactococcal strains affects intracellular enzyme accessibility in Cheddar cheese. SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlights the importance of the autolytic and permeabilization properties of lactic acid bacteria starter strains and their impact on cheese ripening.